Gear pump

ABSTRACT

Means are provided to permit relative axial displacement between one of the two gear wheels and a wall of the pump chamber, whereby the sealing engagement between this wheel and wall is interrupted. A device is operable independently of above-normal pressure in the pump chamber to effect this displacement and thereby establish a free passage through the pump chamber.

United States Patent [191 Svensson Apr. 8, 1975 i 1 GEAR PUMP 148L560 91949 Bakewell 4l8/70 3,4 2 S h' 1 1 Inventor: Sven Hiding Svensson.Lund. R1330? 2532? N222??? 4.8m

Sweden [73] Assignee: Alia-Laval AB, Tumba, Sweden primary J Husar [32]p Aug 20 1973 Assistant Examiner-O. T. Sessions Attorney, Agent, orFirmCyrus S. Hapgood [2]) Appl. No: 389,584

[30] Foreign Application Priority Data [57] ABSTRACT Aug. 1 72 S edenl075 /72 Means are provided to permit relative axial displacementbetween one of the two gear wheels and a wall [52] US. Cl t. 418/169;418/181 of the pump chamber, whereby the sealing engage- [5 I] it 6 6ment between this wheel and wall is interrupted, A de- [58] Fi ld fSearch 418/2 0. 81. 9, vice is operable independently of above-normalprcs- 4l7/430; 425/225. 227 sure in the pump chamber to effect thisdisplacement and thereby establish a free passage through the pump [56]References Cited chamber.

UNITED STATES PATENTS M72357 6/1928 Heitz 418/70 6 Clams 3 Draw figuresA 17 2O 15 2 9a n z2 27 as GEAR PUMP The present invention relates to agear pump comprising a pump housing having a pump chamber provided withfluid inlet and outlet means, and two gear wheels rotatable aroundparallel axes within said pump chamber, said gear wheels being adaptedduring normal operation of the pump to sealingly engage the walls of thepump housing and having intermeshing teeth or similar elements.

Pumps of this kind are used, for example, when a vis cous fluid is to beconveyed through a conduit, as in ice-cream or margarine producingplants.

A problem which has long been of interest in plants comprising gearpumps, especially within the food industry, is that the cleaning of theplants has been made more difficult, particularly due to the presence ofthe pumps. That is, gear pumps have a relatively small capacity which,without special arrangements, makes it impossible to flush cleaningliquid through the plant at a sufficient rate to obtain an efficientcleaning thereof.

Heretofore, the flushing of cleaning liquid through such a plant hasbeen made possible by removing the gear wheels from all of the gearpumps of the plant. However, this has required extra manual labor, whichhas been time consuming and has required specially trained personnel.Another solution of the cleaning problem is to provide the gear pumpswith by-pass conduits adapted to open when the plant is to be flushedthrough with cleaning liquid. However, known plants comprising suchby-pass conduits have not fulfilled the demands of hygiene raised in thefood industry, be cause the by-pass conduits have formed spaces in whichthe treated product has been kept stationary during the normal operationof the plant, and thus growth of bacteria has been possible.

The principal object of the present invention is to eliminate theabove-noted problem and to provide a gear pump arrangement which in asimple way enables plants comprising gear pumps to be cleanedefficiently.

The invention is characterized by a device which is adapted,independently of a pressure in the pump chamber exceeding the normaloperating pressure, to provide for an axial relative displacement of atleast one of the gear wheels and one of the walls of the pump chamber,whereby the sealing engagement between these members displaced inrelation to each other is interrupted and a free passage is establishedthrough the pump chamber, said passage permitting a generally free flowof fluid through the pump chamber between its inlet and outlet. Thearrangement for sealing between the portions of the pump housing can bedesigned in different ways within the scope of the invention. The pumphousing portions are preferably so designed that one of them sealinglysurrounds the other one, whereby ordinary sealing rings can be used.

The invention is applicable to different types of gear pumps and isbased on the idea of creating a leakage past the gear wheels within thewalls of the pump housing when cleaning is to be carried out, suchleakage being prevented during the normal operation of the pump. Thereare gear pumps of a first type in which both gear wheels have radiallyoutwardly directed teeth, and of a second type having a big gear wheelin the form of a rim having radially inwardly directed teeth, a smallgear wheel eccentrically disposed therein and having radially outwardlydirected teeth, and a stationary member having a cross-section in theshape of a sickle and filling out the space within the big gear wheelnot occupied by the small gear wheel. In gear pumps of the latter type,according to the invention, the stationary member and one of the gearwheels are preferably axially fixed in relation to one of the portionsof the pump housing, and the other gear wheel is axially fixed relativeto the other portion of the pump housing. Such an arrangement providesfor a move ment of the gear wheels relative to each other when theportions of the pump housing are moved relative to each other; andaccording to a further development of the invention, the gear pump isprovided with means for restricting the relative movement of theportions of the pump housing, whereby the teeth of the gear wheelsremain intermeshing. In this way, both gear wheels can be kept rotatingduring a cleaning operation and can thus be cleaned efficiently, evenwhen only one of the gear wheels is connected to a driving shaft, as isusually the case. According to a preferred embodiment of the invention,the gear wheel which is not driven is rotatably supported and axiallyfixed to a journal which is rigidly connected to the portion of the pumphousing supporting said stationary member.

The invention will be described more in detail below, reference beingmade to the accompanying drawing.

In the drawing,

FIGS. 1 and 2 are longitudinal, sectional views of a gear pump inaccordance with the invention, and

FIG. 3 is a cross-section taken along line llllll in FIG. 1.

The gear pump shown in the drawing has a pump housing comprising a body1, a cylindrical member 2 connected to the body, and a wall 3 axiallyslidable within the cylindrical member. In FIG. 1, the slidable wall 3engages the body I along a step 4 and together with the body defines apump chamber 5. Sealing rings 6 are provided between the slidable wall 3and the cylindrical member 2 of the pump housing. In the pump chamber 5,which has an inlet 7 and an outlet 8, are two rotatable gear wheels, abig wheel 9 and a small wheel 10. The big gear wheel 9 has the shape ofa toothed rim having radially inwardly directed teeth 11, the spacesbetween the teeth also opening radially outwards. The small gear wheel10, which is disposed within the big gear wheel 9, has the form of anordinary gear wheel, the teeth 12 of which mesh with the inwardlydirected teeth of the big gear wheel 9 along a portion of its periphery.The small gear wheel is thus eccentrically oriented with relation to thebig gear wheel. In the space within the big gear wheel 9 not occupied bythe small gear wheel 10, there is disposed a stationary member 13 havinga cross-section in the form of a sickle. This member 13 is formed by aprotrusion of the slidable wall 3, said wall also having a journal 14 onwhich the small gear wheel 10 is rotatably supported. The small gearwheel 10 is axially fixed relative to said journal 14 by means of a bolt15.

The big gear wheel 9 is supported by a shaft 16 which extends out of thepump housing and is connected to a drive means (not shown). A sealingring 17 is provided between the shaft and the pump housing. The big gearwheel 9 has a number of generally axially extending passages in the formof circumferentially spaced, inclined borings 90, one of which is shownin FIGS. 1 and 2, and another passage in the form of a recess la isprovided in the pump housing, as shown in FIGS. 1-3. The function ofthese passages is to enable the space between the big gear wheel 9 andthe adjacent end wall of the pump chamber to be cleaned efficiently, aswill be described later.

During the operation of the gear pump, a fluid flows from the inlet 7into the spaces between the teeth of the big gear wheel 9 and the smallgear wheel 10 when these spaces are passing the inlet. In order tofacilitate the flowing of the fluid into the spaces between the teeth,the slidable wall 3 has a recess 18 in front ofthe inlet 7, as can beseen in FIG. 1. On both sides of (i.e., radially inside and outside) thestationary member 13, the fluid is then transported by the gear wheelsto the area in front of the outlet 8 where it is pressed out of thespaces between the teeth and further through the outlet 8, owing to thefact that the teeth of the two gear wheels intermesh again in this area.To facilitate the passing of the fluid out of the pump housing, the slidable wall 3 has a recess (not shown) even at the outlet 8. The big gearwheel 9 seals against the portion 1 of the pump housingcircumferentially of its non-toothed portion, and the small gear wheel10 seals against the slidable wall 3.

At the end of the cylindrical portion 2 of the pump housing, there is anend wall 19. A number of bolts 20 extend through this end wall andfurther throughout the entire pump housing, said bolts holding togetherthe different portions of the pump housing. Within the cylindricalportion 2 of the pump housing, there is a partition wall 21 which,together with the slidable wall 3. defines a chamber 22 in thecylindrical portion 2 of the pump housing. A spindle 23 connected to theslidable wall 3 extends through the fixed partition wall 2], saidspindle supporting, on the opposite side of the fixed partition wall, asecond slidable wall 24 which is slidable in the cylindrical portion 2of the pump housing. The wall 24 is attached to the spindle 23 by meansof a nut 25. Sealing rings 26 and 27 are provided between the slidablewall 24 and the cylindrical portion 2 ofthe pump housing. and alsobetween the spindle 23 and the fixed partition wall 21, whereby a sealedchamber 28 is formed between the slidable wall 24 and the fixedpartition wall 21. The two sealed chambers 22 and 28 thus formed in thecylindrical portion 2 of the pump housing are adapted to be connectedalternately to a pressure source (not shown), whereby the spindle 23with the slidable walls 3 and 24 can be adjusted to the desired endposition. Connection means to the pressure source are shown at 29 and30. A guide bar 31 having a square cross section extends from saidsecond slidable wall 24 and out through the end wall 19 of the pumphousing.

As can be seen in FIG. 2, the rightward movement of the slidable walls 3and 24 is restricted by the nut and the end wall 19 of the cylindricalportion of the pump housing. The portions incorporated in the gear pumphave such dimensions that the small gear wheel 10, which moves axiallywith the slidable wall 3 of the pump housing, will not be slid out ofengagement with the big gear wheel 9 when the wall 3 of the pump housingis moved to its extreme right-hand position. The

gear wheels can thus be kept rotating irrespective of the position ofthe slidable walls 3 and 24.

When the different portions of the pump housing have taken theirpositions as shown in FIG. 2, a large amount of liquid (for example,cleaning solution) can flow through the pump from the inlet 7 to theoutlet 8 without being obstructed. The liquid passes from the inlet 7radially inward through the gaps between the teeth of the big gear wheel9 and then radially outward through said gaps in front of the outlet 8.Liquid is also caused to flow through the openings 9a of the big gearwheel 9, in a leftward direction in FIG. 2, into the space between thebig gear wheel 9 and the left end wall of the pump chamber and isdischarged therefrom through the recess 10 in the pump housing, wherebythis space is cleaned also. The flow of the liquid through thesepassages is ensured by the centrifugal force acting on the liquid in theinclined openings during the rotation of the big gear wheel 9.

l claim:

1. A gear pump comprising a housing having walls forming a pump chamber,said chamber having an inlet and an outlet, first and second gear wheelsrotatable about parallel axes within said chamber, said gear wheelshaving intermeshing elements and being adapted during normal operationof the pump to sealingly engage adjacent walls of the pump chamber, oneof said first gear wheel and a first said wall being mounted for axialdisplacement relative to the other of said first wheel and first wall,whereby the sealing engagement between said first wheel and first wallis interrupted, and a device operable independently of an above-normalpressure in the pump chamber to effect said displacement and therebyestablish a free passage through the pump chamber, said passagepermitting a generally free flow of fluid through the pump chamberbetween its inlet and outlet.

2. The gear pump of claim 1, in which said device includes means locatedoutside the pump housing and connected to said first gear wheel, saidmeans being op erable to positively displace the first gear wheel inopposite directions relative to the second gear wheel.

3. The gear pump of claim 1, in which said first wall is movablerelative to a second of said walls in the axial direction of the gearwheels, said first and second walls being sealingly interconnected toenable the pump chamber to expand by movement of said first wall awayfrom said second wall.

4. The gear pump of claim 3, in which one of said first and second wallsis included in a portion of the housing which surrounds the other ofsaid first and second walls.

5. The gear pump of claim 3, in which each of said gear wheels isaxially fixed relative to one of said first and second walls.

6. The gear pump of claim 3, comprising also means for restrictingrelative movement of said first and second walls to maintainintermeshing of the gear wheels.

1. A gear pump comprising a housing having walls forming a pump chamber,said chamber having an inlet and an outlet, first and second gear wheelsrotatable about parallel axes within said chamber, said gear wheelshaving intermeshing elements and being adapted during normal operationof the pump to sealingly engage adjacent walls of the pump chamber, oneof said first gear wheel and a first said wall being mounted for axialdisplacement relative to the other of said first wheel and first wall,whereby the sealing engagement between said first wheel and first wallis interrupted, and a device operable independently of an abovenormalpressure in the pump chamber to effect said displacement and therebyestablish a free passage through the pump chamber, said passagepermitting a generally free flow of fluid through the pump chamberbetween its inlet and outlet.
 2. The gear pump of claim 1, in which saiddevice includes means located outside the pump housing and connected tosaid first gear wheel, said means being operable to positively displacethe first gear wheel in opposite directions relative to the second gearwheel.
 3. The gear pump of claim 1, in which said first wall is movablerelative to a second of said walls in the axial direction of the gearwheels, said first and second walls being sealingly interconnected toenable the pump chamber to expand by movement of said first wall awayfrom said second wall.
 4. The gear pump of claim 3, in which one of saidfirst and second walls is included in a portion of the housing whichsurrounds the other of said first and second walls.
 5. The gear pump ofclaim 3, in which each of said gear wheels is axially fixed relative toone of said first and second walls.
 6. The gear pump of claim 3,comprising also means for restricting relative movement of said firstand second walls to maintain intermeshing of the gear wheels.